Computer systems typically use evacuative cooling systems for temperature control. Using one or more fans, outside air is drawn in through vents, pulled through and around the internal components, over a heat exchanger assembly, and then is pushed out through other vents. Heat generated by the internal components—in particular, the central processing unit (CPU) and graphics processing unit (GPU)—is conducted by heat pipes into the heat exchanger assembly and thereby removed from the system.
In most systems, the CPU and GPU constitute the largest sources of heat loads. For example, in a typical notebook device, the CPU and GPU together can contribute up to 70 watts of thermal power, and up to 100 watts in a high end configuration. The next largest contributor is usually the memory subsystem, which generally peaks at around eight watts. The total system cooling capability of a typically dimensioned notebook is about 85 watts, and so the majority of the cooling capability is directed into the heat exchanger system for the CPU and GPU. Thus, the CPU and GPU present the largest thermal power management challenge, affecting system design, form factors, and component purchasing decisions. In other words, a device's target form factor and implied cooling capabilities can limit a designer's choice of GPU due to assumptions that need to be made about the worst-case thermal effects of both the GPU and CPU.
If the thermal contributions of the computer system's internal components are not mitigated, then the temperatures of those components can increase until either the components self-throttle in order to avoid exceeding their respective temperature limit, or the inability to adequately remove heat from the system causes one or more components to overheat. Overheating can damage internal components, and heat conduction and radiation into the device's chassis and skin (housing) may elevate surface temperatures to the point where the device feels uncomfortably hot to a user.